We propose to continue the Brown Longitudinal Obsessive Compulsive Study (BLOCS), a unique, naturalistic, prospective study of 400 subjects whose primary reason for seeking treatment was OCD, for an additional 5 years of f/u. This will enable us to obtain a minimum of 7 years of f/u on all subjects and to incorporate new assessments and data analysis methods in order to address important unanswered questions while developing a comprehensive picture of the longitudinal course and outcome of OCD. It will provide important new and clinically relevant information about prognosis, rates of remission and relapse, predictors of remission and relapse and treatment received that will in turn have significant implications for public health policy. Our specific aims are to (1) determine the course, stability and outcome of selected OCD phenotypes (2) collect comprehensive treatment data on the long term effects of SRIs, augmenting medications, and cognitive behavior therapy (3) to determine the patterns of course and outcome of a clinical sample of child and adolescents with OCD and compare them to a clinical sample of adults with OCD. Subjects will be evaluated at 1 year intervals with instruments that obtain detailed information on symptom status and severity, diagnostic status, treatment received, psychosocial functioning, and other domains. Since the last submission we have added new assessments that measure stressful life events, underlying mood- and anxiety-related traits, and symptom severity independent of diagnosis and functioning;we have also incorporated new data analysis methods in order to answer important questions about OCD. To have sufficient statistical power to test our hypotheses, 5 more years of prospective observation are needed. The BLOCS data set is unique in its large number of subjects, comprehensiveness of assessment, and length of prospective f/u. This proposal will allow us to more completely investigate the aims and hypotheses of the previously funded grant and to add new, previously unexplored aims and hypotheses generated by findings from BLOCS and other investigators during the past 4 years. Continuation of BLOCS is expected to shed new light on clinically and theoretically important, innovative questions about an understudied major psychiatric disorder, which have not been adequately addressed by previous research.